I don't find toolbars useful at all; I like menus. My wife, when I'm
using a program in front of her, will tell me which toolbar button to
press to do some operation, but I always go straight to the menu and
select the menu item.

The most significant reason for this is that the natural language text
of the menu item is a positive confirmation that the command you're
about to operate is the one you really want. The little icons have no
such association for me. For me, little pictures are not verbs.

Another problem with toolbars is that there is not a lot of
standardization for the icons. Even though some common operations may
have frequently repeated icons in different programs, each program will
usually draw the icon art in a slightly different way, in part to make
it consistent with the internal look of the program, and in part to
avoid violating the copyright of some other program they may have gotten
the idea for the icon from.

While someone may claim you stole his art for a little floppy disk icon,
no one will claim you stole the word "Save" from his program.

For me, toolbars are just wasted space and I'd really like to at least
have the option to note have them appear in a document at all, so I can
have more screen real-estate for useful visible document content.

This is especially important if, like me, you're the kind of user who
leaves a lot of windows open on the screen and flips between windows
frequently. Having the toolbar art change so much is really
distressing. The most important thing to me is that the result of my UI
input be predictable in its result, and I don't have the feeling that
that's the case if I try to use toolbars.